In this study we have analyzed differentiation and function of
CMVpp65-specific CD8+ T cells in paired samples of human pB and BM using
intracellular cytokine and tetramer staining. Overall frequencies of CMV-
pp65-specific T cells were similar in pB compared to BM, however, CMV-specific
CD45RA-CCR7+ Tcm were almost exclusively detectable in BM, which was not
related to a general accumulation of Tcm in BM. In vitro CMV-specific T cells
could be more efficiently expanded from BM than from pB (BM: median 128-fold,
pB: median 72-fold; p=0.001 n=6). CMV-specific CD8+ T cells expanded in vitro
from pB and BM were almost uniformly Tem, whereas both CMV-specific Tem and
Tcm were generated from BM. Higher expression of CXCR4 on BM CMV-specific T
cells compared to pB and on CMV-specific Tcm compared to Tem suggests
involvement of CXCR4 in the accumulation of CMV-specific Tcm in BM. Taken
together, these data show that the BM is a compartment harboring CMV-specific
Tcm which are considered crucial in maintaining long-term immunity and these
data underline the concept of the BM as a secondary immune organ. CMV specific
BM-derived Tcm might be a valuable source for generating T cells for adoptive
transfer.